I'm a big fan of my Samsung chromebook. It's light, has no fan and the battery lasts all day. I find myself taking it to all my meetings rather than my hefty macbook pro.
My personal preference for webdev on the go is the combination of these tools:
It's a browser based IDE with terminal access. $8/month* for unlimited private projects is well worth it. The boxes are fast enough that I find my grunt tasks take a lot less time than my local computer.
At times editing a PSD on the go is unavoidable and this tool is a lifesaver. If you've got an adobe subscription you can use your existing storage (20 gigs I think) to store PSDs in the cloud and edit them in the browser. It's certainly not as feature rich as photoshop, but it can handle large PSDs accurately and allows you to extract colours, fonts, and images easily.
Sometimes having a full linux box to SSH into is valuable, and for $5/month digitial ocean is an easy choice.